IPAT equation

The IPAT equation, though phrased mathematically, is a simple conceptual expression of the factors that create environmental impact. IPAT is an accounting identity stating that environmental impact (I) is the product of three terms: 1) population (P); 2) affluence (A); and 3) technology (T). It is stated I = P x A x T or I=PAT. Generally credited to ecologist Paul Ehrlich, the IPAT formulation arose from a dispute in the early 1970s among the most prominent environmental thinkers of the day about the sources of environmental impact. Ehrlich and John Holdren identified population size and growth as the most urgent IPAT factor, whereas Barry Commoner argued that post-World War II production technologies were the dominant reason for environmental degradation.

Passing over more complex models, IPAT has been chosen by many scholars in both the social and natural sciences as a starting point for investigating interactions of population, economic growth, and technological change. Operationalizing IPAT terms has figured into work on consumption, agriculture, and energy decomposition analysis. IPAT variants have been used by the Intergovernmental Panel on Climate Change (IPCC) in energy-related carbon emission studies. IPAT variants since the 1990s have reversed the original 1970s view of the harmful role of technology. The World Resources Institute studies of industrial ecology reinterpreted IPAT to suggest that given increases in population and affluence, the T term of the IPAT equation then becomes an essential counterweight to P and A requiring environmentally effective technological choices to reduce environmental impact per unit of economic activity.

Further Reading



Chertow, M. (2008). IPAT equation. Retrieved from http://www.eoearth.org/view/article/153641


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